We describe the Monitoring and Checking (MaC) framework which assures the correctness of the current execution at run-time. Monitoring is performed based on a formal specification of system requirements. MaC bridges the gap between formal specification and verification, which ensures the correctness of a design rather than an implementation, and testing, which partially validates an implementation. An important aspect of the framework is a clear separation between implementation-dependent description of monitored objects and high-level requirements specification. Another salient feature is automatic instrumentation of executable code. The paper presents an overview of the framework and two languages to specify monitoring scripts and requirements, and briefly explain our on-going prototype implementation.